1. Field of the Invention
This invention relates to a novel process for producing large sol-gel SiO.sub.2 containing monoliths in which a transition metal is homogeneously distributed throughout on substantially a molecular basis and products obtained by the practice of the novel process.
2. Description of the Prior Art
Prior developments, see copending applications Ser. Nos. 583,741 A24178 and 924,179 all filed Feb. 27, 1984, have shown how to produce rapidly large optically transparent SiO.sub.2 containing monoliths of SiO.sub.2, Li.sub.2 O-SiO.sub.2, Na.sub.2 O-SiO.sub.2 Al.sub.2 O.sub.3 -B.sub.2 O.sub.3 -SiO.sub.2, Al.sub.2 O.sub.3 -SiO.sub.2, Li.sub.2 O-Al.sub.2 O.sub.3 -SiO.sub.2, Li.sub.2 O-Al.sub.2 O.sub.3 -TiO.sub.2 SiO.sub.2 using special drying control chemical additives. The present invention provides a novel process for introducing transition metal elements or compounds into SiO.sub.2 containing sol-gel systems and novel products which are derived from the practice of the invention. The newly discovered process is based upon the discovery and use of mellitic acid, also called benzene hexacarboxylic acid [C.sub.6 (CO.sub.2 H).sub.6 or C.sub.6 (COOH.sub.6 ], whose structural formula may be shown schematically as: ##STR1##